Dermis: Collagen Fibers & Elastic Fibers

Dermis

middle layer of skin

Layers of the dermis

Papillary and Reticular layer

Papillary layer of the dermis

The dermis, made of loose connective tissue, has dermal papillae that interlock with the epidermis and contain capillaries and sensory receptors

Reticular layer of the dermis

Made of dense irregular connective tissue. Contains sweat and sebaceous glands, hair follicles, blood vessels, and nerves. Provides strength and elasticity.

Collagen and elastic fibers in the dermis

Oriented in parallel bundles along routine stress. Collagen provides strength and resists stress. Elastic fibers provide stretch and recoil.

Lines of cleavage (tension lines)

Show the orientation of fiber bundles. Incisions parallel to these lines heal faster. Incisions perpendicular may reopen.

Stretch marks (striae)

Occur when skin stretches too much. Some collagen fibers tear leaving visible marks.

Aging and UV exposure effects on the dermis

Reduce flexibility and thickness of the dermis. Can cause sagging and wrinkles.

Structures in the Dermis NOT in the Epidermis

Blood vessels (epidermis is avascular)

Sweat and sebaceous glands

Hair follicles and arrector pili muscles

Sensory nerve endings

How does the dermis help regulate body temperature?

Blood vessels dilate to release heat and constrict to retain heat. Sweat glands produce sweat which cools the body as it evaporates.

Nerve fibers in the dermis

Extensive network of nerves. Sensory fibers detect pressure, vibration, and cold. Motor fibers control blood flow and gland secretions.

Blood vessels in the dermis

Supply nutrients to the dermis and epidermis. Help regulate body temperature and blood. Large vessels run along the reticular-subcutaneous border. Smaller vessels branch into the dermis and dermal papillae.

Vasoconstriction

Blood vessels narrow, blood moves to deeper structures. Keeps in heat. Skin appears pale in cold.

Vasodilation

Blood vessels widen, more blood near skin surface. Releases heat. Skin may appear flushed.